1. Technical Field
The present invention relates to an electronic timepiece that receives signals transmitted from GPS satellites or other positioning information satellites and displays information.
2. Related Art
The Global Positioning System (GPS) uses GPS satellites (positioning information satellites) that orbit the Earth on known orbits and enables a GPS receiver (GPS device) to determine its own location from these GPS signals. Each GPS satellite carries an atomic clock, and transmits satellite signals that contain time information (GPS time information) expressing the time (GPS time) that is kept by the atomic clock. The GPS time is the same on all GPS satellites, and UTC (Coordinated Universal Time) is determined by correcting the GPS time with the UTC offset (currently +15 seconds), which is the difference between GPS time and UTC. UTC can therefore be determined by receiving a satellite signal from a GPS satellite and acquiring the GPS time, and then correcting the GPS time based on the UTC offset.
Microwave signals (signals in the ultrahigh frequency band) such as satellite signals have a short wavelength and are therefore easily susceptible to the effects of metal. As a result, electronic timepieces (referred to below as GPS timepieces) that obtain the current time from satellite signals received from GPS satellites generally have a plastic case. However, achieving a high quality appearance with a plastic case is difficult. Plastic cases are also easily scratched. As a result, technologies that enable using a metal case as the case of the electronic timepiece while reducing the effect on microwave signal reception have proposed. Japanese Unexamined Patent Appl. Pub. JP-A-2001-27680, for example, teaches a GPS timepiece that disposes the antenna on the outside of the metal case, and Japanese Unexamined Patent Appl. Pub. JP-A-2000-147169 teaches a GPS timepiece that disposes the antenna inside the metal case on the back side of the display unit, and enables sliding the display unit.
However, because the antenna is disposed on the top of the case in the GPS timepiece taught in JP-A-2001-27680, the area that can be used for a functional display (such as displaying the date) is limited and the display lacks balance.
Furthermore, in the GPS timepiece taught in JP-A-2000-147169, antenna sensitivity could drop drastically depending on the position of the antenna relative to the case because the antenna is located inside the metal case. JP-A-2000-147169 also says nothing about an arrangement for suppressing the loss of antenna sensitivity to a sufficiently low level.